Curable compositions are compositions that include thermosettable monomers that can be crosslinked. Crosslinking, also referred to as curing, converts the curable compositions into crosslinked polymers (i.e., a cured product) useful in various fields such as composites, electrical laminates, and coatings because of, among other things, their chemical resistance, mechanical strength, and electrical properties. For example, curable compositions can be used in electronics as protective films, adhesive materials, and/or insulating materials, such as interlayer insulating films.
To be useful for these applications, a cured product of the curable compositions need to provide ease of handling and certain necessary physical, thermal, electrical insulation, and moisture resistance properties. For example, curable compositions having a low dielectric constant, a high solubility, and a low moisture uptake, as well as a high glass transition temperature (Tg), can be desirable combination of properties for electrical applications.
The use of curable compositions in electronic applications can also influence the electrical signals generated in the electronics. Increases in electrical signal frequency in an electronic system (e.g., a computer system) allows for data to be processed at a higher rate. Curable compositions in the vicinity of such electrical signals, however, can exert a large influence on transmission loss of such electrical signals in a high frequency circuit. To minimize this influence, curable compositions having a low dielectric constant and a low dissipation factor, in addition to the other properties discussed herein, are desired.
Curable compositions, however, can be flammable. As such, different approaches have been made to impart flame resistance to the cured products of the curable compositions. Two main approaches have been taken to providing flame resistance. The first is a “Green” approach in which halogen-free compounds are used. The second approach makes use of halogen compounds. Halogenated compounds have been used for decades in the electronic industry to impart flame resistance to electrical and electronic assemblies. For example, tetrabromobisphenol-A (TBBA) has been a workhorse flame resistance in electrical laminates for many years. Halogenated compounds, however, are now being scrutinized by environmental groups due to the possibility of dioxin formation during the incineration of electronic components at their end of life. In many developed countries the burning of the components is regulated and controlled, however, in developing countries, burning is often unregulated, increasing the likelihood of brominated dioxin release into the atmosphere.